I don't think there's any arguing about it. If I'm not mistaken, of all qualified starters, Mikolas had the highest ERA in MLB last season.
Actually, Patrick Corbin had the highest ERA in MLB last season, Mikolas had second worst at 5.35. However, Corbin, of course, didn't have an MLB job this season and was languishing in the Rangers AAA system until an injury 2 days ago.
5.35 ERA from Mikolas sounds like a pipe dream at this point.